Web-Vet TM Neurology Specialists
Paroxysmal Dyskinesia
Paroxysmal dyskinesias are a group of conditions characterized by episodes of abnormal movement that are self-limiting. The term paroxysmal dyskinesia is used to describe the clinical disease. Their infrequent occurrence within an individual and their abrupt nature has meant they appear to have historically been underdiagnosed. The catalyst for the increased awareness of these conditions has been the popularity of the smartphone. Observing these episodes in real time has allowed greater recognition of these conditions and in turn, we are gaining more of an insight into what they actually represent.
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Dystonic head tremor in paroxysmal dyskinesia in 17 dogs (2021–2023)
Dystonic head tremors are described as fine irregular head tremors accompanied by cervical dystonia, truncal or head sway, shifting limb or single limb dystonia along with other movements (see our video above).
In this study, over 40% of dogs diagnosed with paroxysmal dyskinesia manifested a dystonic head tremor. Poodle or Poodle-cross was the most commonly affected breed Neurological examination and advanced imaging, when available, were within normal limits.
The video above shows a dog with dystonic head movements.
Paroxysmal Dyskinesia in Welsh Terriers
A recent study has highlighted a potentially heritable movement disorder in Welsh Terriers.
In this study, the episodes were predominantly characterized by sustained hypertonicity with periods of limb flexion, abnormal head and body posture, with preserved consciousness. Episode duration ranged from 30 s to 30 min (median, 3 min 30 s), with frequency varying widely between dogs. Affected dogs demonstrated a stable to improving clinical course in most cases. A third of dogs exhibited gastrointestinal signs following episodes, including vomiting, diarrhoea, flatulence, and borborygmi similar to Border terrier dogs that have a paroxysmal gluten-sensitive dyskinesia
Dystonia in veterinary neurology
Dystonia refers to an abnormal muscle tone and can be a feature of many disorders including paroxysmal dyskinesia. In this review, the authors propose a classification system based either on a temporal pattern and localisation characteristics as well as another classification based on etiology. In addition, pathophysiology and examples of movement disorders with dystonia as a feature in different species are reviewed.
Above is an example of dystonia as a feature of paroxysmal dyskinesia in a Yorkshire terrier.
Phenotypic Characterisation of Paroxysmal Dyskinesia (PD) in Sphynx Cats
Ten Sphynx cats were included in the study to identify phenotypic features of PD in this breed. All affected cats were <4 years of age at the onset of the episodes . The episodes had a duration of <5 mins in 9/10 cats while episode frequency was variable between and within individual cats. The episodes were characterised by impaired ambulation due to muscle hypertonicity, most commonly affecting the hips and pelvic limbs and shoulders and thoracic limbs. The head and neck, tail, and back and abdomen were also involved in some cats. Sudden movement, excitement and stress were identified as possible triggers for the episodes in three cats. Therapeutic intervention was not attempted in 7/10 cases, although two cats were reported to become free of the episodes while receiving acetazolamide
A knockout mutation associated with juvenile paroxysmal dyskinesia in Markiesje dogs indicates SOD1 pleiotropy
This study of Markiesje dogs (the Dutch Tulip Hound) identified a deficiency in SOD1 leading to early-onset movement disorders with full penetrance (while mutations that lead to SOD1 aggregation cause motor neurone death with variable and age-dependent penetrance as seen in degenerative myelopathy).
Affected pups show severe tetraparesis, dystonia, cramping, and falling over when trying to walk as illustrated in the attached video provided courtesy of Dr. Paul Mandigers from Utrecht University.
Mitochondrial PCK2 Missense Variant in Shetland Sheepdogs with Paroxysmal Exercise-Induced Dyskinesia (PED)
This study describes Shetland Sheepdogs with hypertonic PD triggered by exercise and stress, which is related to a missense variant in the PCK2 gene encoding the mitochondrial phosphoenolpyruvate carboxykinase 2.
Treatment with phenobarbital, diazepam or levetiracetam did not alter the clinical course; treatment with a gluten-free, home-made fresh meat diet in three dogs or a tryptophan-rich, gluten-free, seafood-based diet, stress-reduction, and acetazolamide or zonisamide in the fourth dog correlated with a partial reduction in, or even a complete absence of, dystonic episodes.
Gluten serological testing in various dog breeds with paroxysmal dyskinesia (PD)
This study aimed to evaluate dogs, other than the Border terrier, with PD, for positive gluten serology.
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Fourteen of the 31 dogs tested positive for gluten sensitivity with either gliadin IgG or transglutaminase-2 IgA or both ratios elevated. In seven dogs, serology was classified as questionable with gliadin IgG or transglutaminase ratios mildly elevated. Ten dogs tested negative. According to the owners' reports, five of the dogs that tested positive had no more episodes after changing to a strictly gluten-free diet, with one of the dogs relapsing twice after being fed treats containing gluten. Three dogs had a reduction in episode frequency of >50%, and two dogs had shorter and less intense episodes.
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Canine paroxysmal dyskinesia—a review
Using a clinical classification, three main types of PDs have been distinguished in canine PD: (1) paroxysmal kinesigenic dyskinesia (PKD) that commences after (sudden) movements, (2) paroxysmal non-kinesigenic dyskinesia (PNKD) not associated with exercise and can occur at rest, and (3) paroxysmal exertion-induced dyskinesia (PED) associated with fatigue. An etiological classification of canine PDs includes genetic (proven and suspected), reactive (drug-induced, toxic, metabolic, and dietary), structural (neoplasia, inflammatory, and other structural causes), and unknown causes. In this review, an overview of all reported canine PDs is provided with emphasis on phenotype, genotype, and, where possible, pathophysiology and treatment for each reported canine PD.